Comparison of multiple API techniques for the simultaneous detection of microconstituents in water by on-line SPE-LC-MS/MS

Analytical Methods for the Determination of Pharmaceuticals and Personal Care Products in Solid and Liquid Environmental Matrices: A Review

Among the various compounds regarded as emerging contaminants (ECs), pharmaceuticals and personal care products (PPCPs) are of particular concern. Their continuous release into the environment has a negative global impact on human life. This review summarizes the sources, occurrence, persistence, consequences of exposure, and toxicity of PPCPs, and evaluates the various analytical methods used in the identification and quantification of PPCPs in a variety of solid and liquid environmental matrices. The current techniques of choice for the analysis of PPCPs are state-of-the-art liquid chromatography coupled to mass spectrometry (LC-MS) or tandem mass spectrometry (LC-MS2). However, the complexity of the environmental matrices and the trace levels of micropollutants necessitate the use of advanced sample treatments before these instrumental analyses. Solid-phase extraction (SPE) with different sorbents is now the predominant method used for the extraction of PPCPs from environmental samples. This review also addresses the ongoing analytical method challenges, including sample clean-up and matrix effects, focusing on the occurrence, sample preparation, and analytical methods presently available for the determination of environmental residues of PPCPs. Continuous development of innovative analytical methods is essential for overcoming existing limitations and ensuring the consistency and diversity of analytical methods used in investigations of environmental multi-class compounds.

Understanding common population markers for SARS-CoV-2 RNA normalization in wastewater - A review

Wastewater monitoring and epidemiology have seen renewed interest during the recent COVID-19 pandemic. As a result, there is an increasing need to normalize wastewater-derived viral loads in local populations. Chemical tracers, both exogenous and endogenous compounds, have proven to be more stable and reliable for normalization than biological indicators. However, differing instrumentation and extraction methods can make it difficult to compare results. This review examines current extraction and quantification methods for ten common population indicators: creatinine, coprostanol, nicotine, cotinine, sucralose, acesulfame, androstenedione 5-hydroindoleacetic acid (5-HIAA), caffeine, and 1,7-dimethyluric acid. Some wastewater parameters such as ammonia, total nitrogen, total phosphorus, and daily flowrate were also evaluated. The analytical methods included direct injection, dilute and shoot, liquid/liquid, and solid phase extraction (SPE). Creatine, acesulfame, nicotine, 5-HIAA and androstenedione have been analysed by direct injection into LC-MS; however, most authors prefer to include SPE steps to avoid matrix effects. Both LC-MS and GC-MS have been successfully used to quantify coprostanol in wastewater, and the other selected indicators have been quantified successfully with LC-MS. Acidification to stabilize the sample before freezing to maintain the integrity of samples has been reported to be beneficial. However, there are arguments both for and against working at acidic pHs. Wastewater parameters mentioned earlier are quick and easy to quantify, but the data does not always represent the human population effectively. A preference for population indicators originating solely from humans is apparent. This review summarises methods employed for chemical indicators in wastewater, provides a basis for choosing an appropriate extraction and analysis method, and highlights the utility of accurate chemical tracer data for wastewater-based epidemiology.

Rapid Identification of 44 Steroids in Human Urine Samples using HPLCESI- QTOF-MS

Objective:

Detailed analysis of un-processed and un-derivatized free and conjugated urinary steroids is useful to avoid miscalculations and to diagnose sports doping and adrenal problems, including abnormal steroidogenesis, congenital deficiency of related enzymes, cancer, and other disease conditions. Hence, the present study was conducted to develop a soft ionization method to identify the maximum number of urinary steroids using ultra-performance liquid chromatography coupled with quadrupole time of flight mass spectrometer (HPLC–Q-TOF-MS).

Material and Methods:

HPLC–Q-TOF-MS was carried out for the qualitative detection of steroids and their conjugates in urine samples. The method provides high sensitivity and fast analysis of steroids and their glucuronides without hydrolysis or sample preparation or extraction of steroids.

Results:

Using the method, 44 steroids belonging to C-18, C-19, and C-21 classes and their conjugates were resolved and identified using positive and negative modes of ionizations by their characteristic ionization and collision energy induced dissociation behaviors.

Conclusion:

The method is time-saving and good to compare samples from different peoples with control or healthy ones as it does not require any kind of pre-treatment or sample processing. It provides a complete picture of steroids metabolism and catabolism. It can be good for doping control or to explore the effects of other drugs. However, in qualitative analysis, one may miss the significant information unless direct methods of steroids analysis to be employed.

LC-HRMS Metabolomics for Untargeted Diagnostic Screening in Clinical Laboratories: A Feasibility Study

Today’s high-resolution mass spectrometers (HRMS) allow bioanalysts to perform untargeted/global determinations that can reveal unexpected compounds or concentrations in a patient’s sample. This could be performed for preliminary diagnosis attempts when usual diagnostic processes and targeted determinations fail. We have evaluated an untargeted diagnostic screening (UDS) procedure. UDS is a metabolome analysis that compares one sample (e.g., a patient) with control samples (a healthy population). Using liquid chromatography (LC)-HRMS full-scan analysis of human serum extracts and unsupervised data treatment, we have compared individual samples that were spiked with one xenobiotic or a higher level of one endogenous compound with control samples. After the use of different filters that drastically reduced the number of metabolites detected, the spiked compound was eventually revealed in each test sample and ranked. The proposed UDS procedure appears feasible and reliable to reveal unexpected xenobiotics (toxicology) or higher concentrations of endogenous metabolites. HRMS-based untargeted approaches could be useful as preliminary diagnostic screening when canonical processes do not reveal disease etiology nor establish a clear diagnosis and could reduce misdiagnosis. On the other hand, the risk of overdiagnosis of this approach should be reduced with mandatory biomedical interpretation of the patient’s UDS results and with confirmatory targeted and quantitative determinations.

Recent developments in atmospheric pressure photoionization-mass spectrometry

Recent developments in atmospheric pressure photoionization (APPI), which is one of the three most important ionization techniques in liquid chromatography-mass spectrometry, are reviewed. The emphasis is on the practical aspects of APPI analysis, its combination with different separation techniques, novel instrumental developments - especially in gas chromatography and ambient mass spectrometry - and the applications that have appeared in 2009-2014. © 2015 Wiley Periodicals, Inc. Mass Spec Rev 36:423-449, 2017.

Rapid determination of six carcinogenic primary aromatic amines in mainstream cigarette smoke by two-dimensional online solid phase extraction combined with liquid chromatography tandem mass spectrometry

A fully automated, rapid, and reliable method for simultaneous determination of six carcinogenic primary aromatic amines (AAs), including o-toluidine (o-TOL), 2, 6-dimethylaniline (2, 6-DMA), o-anisidine (o-ASD), 1-naphthylamine (1-ANP), 2-naphthylamine (2-ANP), and 4-aminobiphenyl (4-ABP), in mainstream cigarette smoke was established. The proposed method was based on two-dimensional online solid phase extraction combined with liquid chromatography tandem mass spectrometry (SPE/LC-MS/MS). The particulate phase of the mainstream cigarette smoke was collected on a Cambridge filter pad and pretreated via ultrasonic extraction with 2% formic acid (FA), while the gas phase was trapped by 2% FA without pretreatment for determination. The two-dimensional online SPE comprised of two cartridges with different absorption characteristics was applied for sample pretreatment. Analysis was performed by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) under multiple reaction monitoring mode. Each sample required about 0.5h for solid phase extraction and analysis. The limit of detections (LODs) for six AAs ranged from 0.04 to 0.58ng/cig and recoveries were within 84.5%-122.9%. The relative standard deviations of intra- and inter-day tests for 3R4F reference cigarette were less than 6% and 7%, respectively, while no more than 7% and 8% separately for a type of Virginia cigarette. The proposed method enabled minimum sample pretreatment, full automation, and high throughput with high selectivity, sensitivity, and accuracy. As a part of the validation procedure, fifteen brands of cigarettes were tested by the designed method.

Critical assessment of the ubiquitous occurrence and fate of the insect repellent N,N-diethyl-m-toluamide in water

The insect repellent diethyltoluamide (DEET) is among the most frequently detected organic chemical contaminants in water across a wide range of geographies from around the world. These observations are raising critical questions and increasing concerns regarding potential environmental relevance, particularly when the emergence of severe neurological conditions attributed to the Zika virus has increased the use of insect repellents. After dermal application, DEET is washed from the skin when bathing and enters the municipal sewer system before discharge into the environment. Mainly measured by gas chromatography or liquid chromatography coupled to mass spectrometry (GC-MS or LC-MS), more than 200 peer-reviewed publications have already reported concentrations of DEET ranging ng/L to mg/L in several water matrices from North America, Europe, Asia, Oceania, and more recently Africa and South America. While conventional wastewater treatment technology has limited capacity of removal, advanced technologies are capable of better attenuation and could lower the environmental discharge of organic contaminants, including DEET. For instance, adsorption on activated carbon, desalinating membrane processes (nanofiltration and reverse osmosis), ozonation, and advanced oxidation processes can achieve 50% to essentially 100% DEET attenuation. Despite the abundant literature on the topic, the ubiquity of DEET in the environment still raises questions due to the apparent lack of obvious spatio-temporal trends in concentrations measured in surface water, which does not fit the expected usage pattern of insect repellents. Moreover, two recent studies showed discrepancies between the concentrations obtained by GC-MS and LC-MS analyses. While the occurrence of DEET in the environment is well established, the concentrations reported should be interpreted cautiously, considering the disparities in methodologies applied and occurrence patterns observed. Therefore, this manuscript provides a critical overview of the origin of DEET in the environment, the relevant analytical methods, the occurrence reported in peer-reviewed literature, and the attenuation efficacy of water treatment processes.

Charge Exchange Reaction in Dopant-Assisted Atmospheric Pressure Chemical Ionization and Atmospheric Pressure Photoionization

The efficiencies of charge exchange reaction in dopant-assisted atmospheric pressure chemical ionization (DA-APCI) and dopant-assisted atmospheric pressure photoionization (DA-APPI) mass spectrometry (MS) were compared by flow injection analysis. Fourteen individual compounds and a commercial mixture of 16 polycyclic aromatic hydrocarbons were chosen as model analytes to cover a wide range of polarities, gas-phase ionization energies, and proton affinities. Chlorobenzene was used as the dopant, and methanol/water (80/20) as the solvent. In both techniques, analytes formed the same ions (radical cations, protonated molecules, and/or fragments). However, in DA-APCI, the relative efficiency of charge exchange versus proton transfer was lower than in DA-APPI. This is suggested to be because in DA-APCI both dopant and solvent clusters can be ionized, and the formed reagent ions can react with the analytes via competing charge exchange and proton transfer reactions. In DA-APPI, on the other hand, the main reagents are dopant-derived radical cations, which favor ionization of analytes via charge exchange. The efficiency of charge exchange in both DA-APPI and DA-APCI was shown to depend heavily on the solvent flow rate, with best efficiency seen at lowest flow rates studied (0.05 and 0.1 mL/min). Both DA-APCI and DA-APPI showed the radical cation of chlorobenzene at 0.05-0.1 mL/min flow rate, but at increasing flow rate, the abundance of chlorobenzene M(+.) decreased and reagent ion populations deriving from different gas-phase chemistry were recorded. The formation of these reagent ions explains the decreasing ionization efficiency and the differences in charge exchange between the techniques. Graphical Abstract ᅟ.

Fast-Target Analysis and Hourly Variation of 60 Pharmaceuticals in Wastewater Using UPLC-High Resolution Mass Spectrometry

A fast and sensitive monitoring method for trace pharmaceuticals in the environment is vital because many of these compounds are ubiquitous, persistent, and biologically active with recognized endocrine-disruption and pharmacological functions. A rapid and reliable ultra high-performance liquid chromatography combined with tandem mass spectrometry was developed in the present study to simultaneously identify, confirm, and quantify 60 target pharmaceuticals in wastewater samples. The method uses a sub-2 µm particle column for separating target compounds, which were subsequently quantified with the mass spectrometer. Using this high-throughput analysis method, a single injection could provide results within 5 min for the pharmaceuticals. All of the target compounds were analyzed by the multiple-reaction monitoring with 15-ms fast polarity switching. Both intraday and interday precision analyses indicate excellent coefficient of variability. To evaluate the performance of the method, a standard solution (100 and 1000 ng L(-1)) was spiked into complex wastewater samples. The tailing factor and peak width were also monitored and adjusted for optimizing peaks from the ultra high-performance liquid chromatograph. Of the target pharmaceuticals in wastewater of a sewage-treatment plant analyzed on an hourly basis, only 17 compounds were detected, and others were lower than the method detection limits. Acetaminophen, cimetidine, and iopromide were all detected at >1 μg L(-1), and their concentration profiles were similar to that of a nonsteroidal anti-inflammatory drug detected in wastewater. Other noticeable pharmaceuticals were sulfamethoxazole and trimethoprim. Sources of pharmaceuticals in wastewater are briefly discussed.

Detection of dihydroxycholesterols in human plasma using HPLC-ESI-MS/MS

We report a straightforward sample preparation procedure and a direct liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) method for the analysis of 7alpha,25-dihydroxycholesterol (7α25-OHC) and 7alpha,27-dihydroxycholesterol (7α27-OHC). By applying a slow protein precipitation approach using cold ethanol, we were able to detect and quantify 7α25-OHC and 7α27-OHC in a fast and reliable manner. The average concentrations from 20 healthy individuals were determined to be 0.21±0.05nM for 7α25-OHC and 3.4±0.1nM for 7α27-OHC. In addition, we are the first to report the average degrees of esterification (n=8) to be 73.8% and 82% for 7α25-OHC and 7α27-OHC, respectively. Using the established method, we achieved the sensitivity sufficient for detecting low abundant dihydroxylated oxysterols in healthy individuals. This result should enable extension of these studies towards a comprehensive analysis of oxysterol levels under disease conditions.

Predicting trace organic compound breakthrough in granular activated carbon using fluorescence and UV absorbance as surrogates

This study investigated the applicability of bulk organic parameters like dissolved organic carbon (DOC), UV absorbance at 254 nm (UV254), and total fluorescence (TF) to act as surrogates in predicting trace organic compound (TOrC) removal by granular activated carbon in water reuse applications. Using rapid small-scale column testing, empirical linear correlations for thirteen TOrCs were determined with DOC, UV254, and TF in four wastewater effluents. Linear correlations (R(2) > 0.7) were obtained for eight TOrCs in each water quality in the UV254 model, while ten TOrCs had R(2) > 0.7 in the TF model. Conversely, DOC was shown to be a poor surrogate for TOrC breakthrough prediction. When the data from all four water qualities was combined, good linear correlations were still obtained with TF having higher R(2) than UV254 especially for TOrCs with log Dow>1. Excellent linear relationship (R(2) > 0.9) between log Dow and the removal of TOrC at 0% surrogate removal (y-intercept) were obtained for the five neutral TOrCs tested in this study. Positively charged TOrCs had enhanced removals due to electrostatic interactions with negatively charged GAC that caused them to deviate from removals that would be expected with their log Dow. Application of the empirical linear correlation models to full-scale samples provided good results for six of seven TOrCs (except meprobamate) tested when comparing predicted TOrC removal by UV254 and TF with actual removals for GAC in all the five samples tested. Surrogate predictions using UV254 and TF provide valuable tools for rapid or on-line monitoring of GAC performance and can result in cost savings by extended GAC run times as compared to using DOC breakthrough to trigger regeneration or replacement.

Evaluation of the optimization space for atmospheric pressure photoionization (APPI) in comparison with APCI

The usefulness of atmospheric pressure photoionization (APPI) is difficult to evaluate for unknowns due to the fragmented literature. Specifically, the variation of dopants with a wide set of compounds or the use of APPI in the negative mode have rarely been explored. Thirty compounds were selected that were not suitable for ESI with a wide variety of functional groups and investigated with atmospheric pressure chemical ionization (APCI) and APPI in the positive and negative ion modes. The influence of the mobile phase (eluents containing acetonitrile or methanol) and--for APPI--four different dopants (acetone, chlorobenzene, toluene, and toluene/anisole) were explored. Stepwise variation of the organic mobile phase allowed to elucidate the ionization mechanism. Atmospheric pressure photoionization was especially useful for compounds, where the M(●+) and not the [M + H](+) was formed. The dopants chlorobenzene and anisole promoted the formation of molecular ions M(●+) for about half of the compounds, and its formation was also positively influenced by the use of mobile phases containing methanol. In the negative ion mode, APPI offered no advantage toward APCI. Best results were generally achieved with the dopant chlorobenzene, establishing that this dopant is suitable for a wide set of compounds. For one quarter of the compounds, significantly better results were achieved with mobile phases containing methanol for both APPI and APCI than those with acetonitrile, but only in the positive mode. With either of the methods--APPI or APCI--about 10% of the compounds were not detected. Strategies to get results quickly with difficult unknowns will be discussed.

Matrix effect during the membrane-assisted solvent extraction coupled to liquid chromatography tandem mass spectrometry for the determination of a variety of endocrine disrupting compounds in wastewater

Membrane-assisted solvent extraction (MASE) coupled to liquid chromatography-triple quadrupole mass spectrometry (LC-MS/MS) was studied for the determination of a variety of emerging and priority compounds in wastewater. Among the target analytes studied certain hormones (estrone (E1), 17β-estradiol (E2), androsterone (ADT), 17α-ethynyl estradiol (EE2), diethylstilbestrol (DES), equilin (EQ), testosterone (TT), mestranol (MeEE2), 19-norethisterone (NT), progesterone (PG) and equilenin (EQN)), alkylphenols (APs) (4-tert-octylphenol (4tOP), nonylphenol technical mixture (NPs) and 4n-octylphenol (4nOP)) and BPA were included. The work was primarily focused in the LC-MS/MS detection step, both in terms of variable optimization and with respect to the matrix effect study. Both, electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) were assessed both in the negative and positive mode, including the optimization of MS/MS operating conditions. The best results were obtained, in most of the cases, for ESI using 0.05% ammonium hydroxide as buffer solution in the mobile phase, composed with methanol and water. Under optimum detection conditions, matrix effect during the detection step was thoroughly studied. Dilution, correction with deuterated analogues and clean-up of the extracts were evaluated for matrix effect correction. Clean-up with Florisil together with correction with deuterated analogues provided the most satisfactory results, with apparent recoveries in the 57-136% range and method detection limits in the low ngL(-1) level for most of the analytes. For further validation of the method, two separated extraction procedures, the above mentioned MASE, and conventional solid phase extraction (SPE) were compared during the analysis of real samples and comparable results were successfully obtained for E1, E2, EE2, DES, NT, TT, EQ, PG, BPA, ADT, 4nOP, 4tOP, NPs and EQN.

RP-LC and TLC Densitometric Determination of Paracetamol and Pamabrom in Presence of Hazardous Impurity of Paracetamol and Application to Pharmaceuticals

Two simple, accurate and reproducible methods were developed and validated for the simultaneous determination of paracetamol (PARA) and pamabrom (PAMB) in pure form and in tablets. The first method was based on reserved-phase high-performance liquid chromatography, on a Thermo Hypersil ODS column using methanol:0.01 M sodium hexane sulfonate:formic acid (67.5:212.5:1 v/v/v) as the mobile phase. The flow rate was 2 mL/min and the column temperature was adjusted to 35 °C. Quantification was achieved with UV detection at 277 nm over concentration range of 100–600 and 4–24 μg/mL, with mean percentage recoveries were found to be 99.90 ± 0.586 and 99.26 ± 0.901 for PARA and PAMB, respectively. The second method was based on thin-layer chromatography separation of PARA and PAMB followed by densitometric measurement of the spots at 254 nm and 277 nm for PARA and PAMB respectively. Separation was carried out on aluminum sheet of silica gel 60F₂₅₄ using dichloromethane:methanol:glacial acetic acid (7.5:1:0.5 v/v/v) as the mobile phase over concentration range of 1–10 and 0.32–3.20 μg per spot, with mean percentage recovery of 100.52 ± 1.332 and 99.71 ± 1.478 for PARA and PAMB, respectively. The methods retained their accuracy in presence of up to 50% of P-aminophenol and could be successfully applied in tablets.

Carbon disulfide as a dopant in photon-induced chemical ionization mass spectrometry

RATIONALE

The addition of a dopant to an Atmospheric Pressure PhotoIonization (APPI) source of a mass spectrometer has been shown to enhance the degree of analyte ionization. A series of different dopants has been successfully utilized; however, there has been very little published on the characteristics of a good dopant. We have proposed carbon disulfide (CS2) as a novel new dopant based on its absorption cross-section for the VUV photon's energy used and its unique gas-phase ion chemistry, notably the fact that it does not contain a proton.

METHODS

The ability of CS2 to enhance the ionization effectiveness of APPI was tested by using a group of compounds that have different proton affinities (PAs) and electron affinities (EAs). These results were compared to results obtained using the commonly used dopants, toluene and anisole. Particular attention was paid to the formation of [M](+) ions relative to [M+H](+) ions. Mass spectra were collected using a Waters Quattro Premier liquid chromatography/tandem mass spectrometry (LC/MS/MS) system equipped with a commercial Photomate™ photoionization source.

RESULTS

The results show that CS2 increases the ionization efficiency of most of the analytes studied in this work comparably to toluene and anisole. CS2 promotes both ionization routes of [M](+) and [M+H](+). In addition, due to the higher ionization energy (IE) of CS2 (10.01) compared to the IEs of toluene (8.83) and anisole (8.20), CS2 can enhance the ionization efficiency of analytes that cannot be enhanced with toluene and anisole.

CONCLUSIONS

We have determined that CS2 is a viable dopant for use in APPI sources. For some analytes, significant [M+H](+) ion signals are observed; therefore, the donated proton must come from either water clusters or solvents. In addition, CS2 promotes the ionization of analytes with low PAs and higher IEs than that of toluene and anisole.

LC-MS analysis of estradiol in human serum and endometrial tissue: Comparison of electrospray ionization, atmospheric pressure chemical ionization and atmospheric pressure photoionization

Accurate measurement of estradiol (E2) is important in clinical diagnostics and research. High sensitivity methods are critical for specimens with E2 concentrations at low picomolar levels, such as serum of men, postmenopausal women and children. Achieving the required assay performance with LC-MS is challenging due to the non-polar structure and low proton affinity of E2. Previous studies suggest that ionization has a major role for the performance of E2 measurement, but comparisons of different ionization techniques for the analysis of clinical samples are not available. In this study, female serum and endometrium tissue samples were used to compare electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization (APPI) in both polarities. APPI was found to have the most potential for E2 analysis, with a quantification limit of 1 fmol on-column. APCI and ESI could be employed in negative polarity, although being slightly less sensitive than APPI. In the presence of biological background, ESI was found to be highly susceptible to ion suppression, while APCI and APPI were largely unaffected by the sample matrix. Irrespective of the ionization technique, background interferences were observed when using the multiple reaction monitoring transitions commonly employed for E2 (m/z 271 > 159; m/z 255 > 145). These unidentified interferences were most severe in serum samples, varied in intensity between ionization techniques and required efficient chromatographic separation in order to achieve specificity for E2.

Uptake and depuration of pharmaceuticals in reclaimed water by mosquito fish (Gambusia holbrooki): a worst-case, multiple-exposure scenario

Previous studies showed that caffeine, diphenhydramine, and carbamazepine were bioconcentrated by mosquito fish (Gambusia holbrooki) from freshwater bodies directly affected by reclaimed water. To understand the uptake, depuration, and bioconcentration factors (BCFs) under the worst-case conditions, the authors exposed 84 mosquito fish to reclaimed water under static renewal for 7 d, followed by a 14-d depuration phase in clean water. Characterization of the exposure media revealed the presence of 26 pharmaceuticals, whereas only 5 pharmaceuticals-caffeine, diphenhydramine, diltiazem, carbamazepine, and ibuprofen-were present in the organisms after only 5 h of exposure. Caffeine, diltiazem, and carbamazepine were quickly taken up by mosquito fish following a similar uptake curve. Diphenhydramine and ibuprofen, on the other hand, were more gradually taken up by mosquito fish but were also eliminated fairly quickly, resulting in the 2 shortest depuration half-lives at 34 h and 32 h, respectively. For comparison, BCFs based on rate constants (BCFb ), steady-state concentrations (BCFa ), and saturation-state concentrations (BCFc ) were calculated. Values of BCFb ranged from 0.23 to 29 and increased in the order of caffeine < carbamazepine < diltiazem < diphenhydramine < ibuprofen. Values of BCFa and BCFc ranged from 2.0 to 28 and increased in the order of carbamazepine < caffeine < diltiazem < diphenhydramine < ibuprofen. This is the first study using a nonartificial exposure-treated wastewater matrix to generate pharmacokinetic data for pharmaceutical mixtures in aquatic organisms. Environ Toxicol Chem 2013;32:1752-1758. © 2013 SETAC.